Appendix and γM-antibody formation: VII. Rosette-forming cells in rabbits immunized with sheep erythrocytes

After intravenous immunization with sheep red blood cells the rabbit spleen shows a sharp rise in the number of plaque-forming cells but there is no detectable rise in PFC in the appendix or mesenteric lymph node of the same animals. Repeated immunization via an appendicostomy blind loop results in virtually no local PFC and only a small rise in splenic PFC.In lethally irradiated animals neither thymocytes nor appendix cells alone restore the splenic PFC response. Simultaneous injection of the two cell types restores both direct and indirect plaque formation. The injected cells were labeled with tritiated adenosine and a standard rosette assay for specific antigen-binding cells applied to recipients' spleen cells following immunization. Rosettes appeared by 3 days after immunization whether thymocytes or appendix cells were labeled. Labeled rosettes were observed only in animals receiving labeled appendix cells.This result demonstrates the presence of rosette forming cell precursors in rabbit appendix cell populations and suggests that the cells of gut-associated lymphoid tissues include antibody-forming cell precursors which are normally seeded to the spleen and draining lymph nodes.